In a manufacturing process of aluminum hard disks, glass disks, wafers, photo-masks or liquid crystal glass substrates, there is performed a precise polishing, so-called polishing process, using various abrasive grains such as silicon oxide, alumina and eerie in order to finish a surface of the aforementioned aluminum hard disks and so on with extremely high precision. Abrasive grains and polishing dust adhere to the surface polished in the polishing process. In order to remove them, sufficient cleaning has to be performed subsequently.
ultrasonic cleaning and water jet cleaning are known. However, scrub cleaning with a sponge roller made of a polyvinyl acetal-based porous material is widely employed in order to achieve a high cleaning effect and to reduce damages on the substrate. Further, DI water as well as various chemicals suitable for particular substrates such as acids, alkalis and solvents is usually used as a cleaning fluid. For instance, as a cleaning fluid for silicon wafers, a mixed solution of ammonia water and aqueous hydrogen peroxide, dilute hydrofluoric acid, and a mixed solution of hydrochloric acid and aqueous hydrogen peroxide are known.
Among sponge rollers made of a polyvinyl acetal-based porous material, cylindrical brush rollers having a large number of projections on a circumferential surface thereof are widely used for the above-described cleaning, where top portions of the projections are continuously brought into contact with a cleaning surface of en object to be cleaned while the sponge roller is rotated to thereby obtain a good cleaning effect (U.S. Pat. No. 4,566,911). Because only the projections are brought into contact with the object to be cleaned, friction is less, compared to a sponge roller with a flat surface, so that damages on the object to be cleaned are less, and further there is an advantage that dirt passes easily through between the projections together with the cleaning fluid to be removed from the object to be cleaned.
Cleaning devices dedicated to particular substrates are usually used in a cleaning process. It is common among all of the devices that a central core connected to a rotation driving part is covered with a cleaning sponge roller, and the sponge roller is rotated together with the central core, while keeping top portions of projections of the roller into contact with an object to be cleaned.
There are devices where a cleaning fluid is fed through a nozzle or the like to an upper or side portion of an object to be cleaned or of a sponge roller. It is also performed to supply a cleaning fluid to an inside of the sponge roller from the inside of the central core to attain better cleaning capability. In the latter case, the central core has a hollow cylindrical shape, and the cleaning fluid is introduced from one end of the central core, supplied to the sponge roller through holes communicating between the hollow portion and an outer surface of the central core, and then flows out to the outer surface of the sponge roller.
U.S. Pat. No. 6,240,588 discloses a brush core which is characterized by having a plurality of first holes aligned in a straight line in an axial direction of the core and a plurality of second holes aligned in a straight line in the axial direction of the core, in which the first hole group and the second hole group are alternately located, the first hole group alternate with the second hole group in a repeated manner around the core, and the first hole group and the second hole group are located in grooves recessed from the outer surface of the core. A bore at the center of the core has a diameter of 0.060 to 0.35 inch (1.524 to 8.89 mm).
U.S. Pat. No. 6,543,084 discloses a brush core made of an elongated member, in which the elongated member has a plurality of fluid discharge surfaces around and remotete from its center axis, a plurality of the fluid discharge surfaces being provided with a space therebetween, the elongated member has, at a center thereof, a fluid supply bore with a diameter of 0.060 to 0.35 inch (1.524 to 8.89 mm), and a plurality of holes communicating between the fluid supply bore and the fluid discharge surfaces. Each of a plurality of the holes communicating between the fluid supply bore and the fluid discharge surfaces has a diameter of 0.005 to 0.092 inch (0.127 to 2.34 mm).
U.S. Pat. No. 6,308,369 discloses a wafer cleaning device hiving a brush assembly comprising a brush core in which channels are cut along a surface in an axial direction thereof, a first cylindrical sleeve which is concentric with the brush core, and a second sleeve (main brush body), wherein the channels allow a fluid to flow in the axial direction of the brush core and to the first and second sleeves.
U.S. Pat. Nos. 6,247,197 and 5,806,126 disclose a device comprising a cleaning brush mounted thereon.
WO2005/065849 discloses a central core for a cleaning sponge roller capable of uniformly supplying a cleaning fluid to the sponge roller and quickly completing replacement of cleaning fluids at the time of switching the cleaning fluids. Absolute sizes and relative sizes of bore extending in an axial direction of the central core and a plurality of the small holes communicating to a circumferential outer surface of the central core are defined. A plurality of the small holes are distributed in a circumferential direction and the axial direction of the central core and arranged on straight lines in the axial direction, wherein the small holes disposed on one of the straight lines and the small holes disposed on a straight line adjacent to the aforesaid straight line are arranged on common circumferences of the central core, grooves recessed from the circumferential outer surface of the central core are formed in the axial direction of the central core, and the small holes are open in the grooves.